Help with immersion heater

[leiadad]

Hi I have had problem with a 3 phase immersion heater, I installed it into a gravity system about 3 months ago and it stopped working after about a month. It was installed into an existing gravity cylinder which is on bottom floor of a large office block. The cwsc is in roof space and is the size of a large room. The cylinder also has flow and return going to it but boiler system only provides heat for cylinder in winter months as is not zoned. The only thing I done was replace the cylinder which the electricians who were doing wiring on job had supplied. The sparks are now blaming me for the fact the immersion is not working, saying that the cylinder must have run out of water and the immersion has burnt out which I can't see how is possible. The cylinder has a secondary rerun as well. There has never been a complaint of air coming out any taps just that there is no hot water. The immersion is also on some type of electrical breaker. Any advice would be great

 

[leiadad]

Sorry I made mistake in first thread and said I replaced cylinder, I meant to say I replaced cylinder immersion heater

 

[Chuck]

Any advice would be great

What make / model of immersion heater? Can you provide photographs of the wiring when it was in situ. There should also be a rating plate. Also, some good clear close-ups of the failed unit including the terminals.

Do you have a multimeter available?

 

[leiadad]

I have not been back to job chuck as yet, there is some other electricians going back to it next week, the main dispute is if it was my fault or the sparks fault or if it was a dodgy immersion heater. The company who supplied it seem to be taking no responsibility as they said the only way it could burn out is if the cylinder ran out of water which as far as I am concerned is impossible, all I need to know if I am missing something here, apparently the sparks checked it all out and the company had said with the checks spark had done was it had burnt out. The only thing I can think of is disruption to main going into cwsc then secondary pump sucking some water out cylinder after draining cwsc the size of a room dry, but as I said in first post there have been no complaints of air coming from taps with no water. Even if that did happen the secondary is higher up on cylinder than the immersion and would still be submerged. The immersion is is a 9 kw immersion which has three seperate heaters on it which work independently of each other and at least one of them is still working. The only advice I need if anyone can help is wether there is any chance possibe that tank can run dry

 

[leiadad]

I have had to weld this immersion on as the thread was not in good condition prior to me getting there, and as far as I have been told the immersion cost 500 pound as is comercia style immersion so if that immersion has to come out it would be as well changing full cylinder

 

[Chuck]

I have had to weld this immersion on as the thread was not in good condition prior to me getting there, and as far as I have been told the immersion cost 500 pound as is comercia style immersion so if that immersion has to come out it would be as well changing full cylinder

If you are an experienced plumber (and as a GSR you probably are) and can't see that its possible for the tank to have run dry it probably didn't. It'll be up to whoever claims that's what happened to explain how, on the balance of probabillities, that is what happened and that what you did to the system caused it to happen.

There are, IMO, other more likely explanations to be explored.

Firstly, it is always possible for a manufacturing defect to cause premature failure of a device like an immersion heater. It's unlikely (if it is a decent make) but you are asking here because something unusual has happened.

When you said you 'had to weld this immersion on as the thread was not in good condition' do you mean you had to weld in a new flange/boss to renew the thread or did weld the immersion heater directly? If the latter, did you do it in a way approved by the MI?

If the electrician made a mistake they may have wired the heater incorrectly, e.g. applying ~415V to some of the elements instead of ~240 volts. Was the electrician experienced and qualified to work on this sort of (commercial) installation? If it were me, I'd not want the wiring touched until it had been photographed and inspected by an independent electrician. There should be cutout(s) on the immersion heat that trip under fault conditions such as no water or incorrect wiring. You need a record of the state of those cutouts before someone resets them.

Be polite but careful what you say to the other parties in these circumstances. Don't say there was "No hot water." when you mean "There was flow from the hot water taps but it was at low temperature". Make sure 'evidence' is carefully collected and kept safely.

 

[ShaunCorbs]

I'm too worried about how your welded it in (soldered) if this is the case it's a big Nono and a major bodge, commercial 3 phase immersion normally come with a flange style fitmemt

Do you know if it's been on constant since the sparks wired it up ?

Also I would be confused why there using an indirect style cylinder directly as this puts more strain on the immersion elements as there on for long periods and not just as a back up / booster

Also gas is cheaper to run than electric think it's 6p vs 15p per kw (ish)

@Chuck

3 phase is 3 x 240v and normally no neutral or one neutral

It's very unlikely they would accidentally connect 2 or 3 phases to one side of the immersion to overload and blow

Be more likely that the phases are unbalanced (more load on one side causing a drop)

But your best asking on the sparks forum for this as your getting towards my knowledge limit

Or maybe lee could help

@leesparkykent

 

[leiadad]

The immersion has a thread on it which no matter how many times it was put on would not thread on as most of female thread on cylinder was no longer there, I said welded when I meant it had to say soldered to stop any leaking, your right it prob was a botch job. I had explained this to customer who wanted me to solder it as didn't want to replace cylinder at the time. The system is indirect but it is not zoned which is something that we are going to speak to customer about, the immersion is only used in summer months

 

[leiadad]

The immersion worked for a few weeks after it was put in and all was working fine for a while, when I am up with sparks next week I will try and get some pictures and post them on

 

[ShaunCorbs]

I would say immersion over used / lifespan

 

[leesparkykent]

If it all worked fine for a few weeks before packing up I would think the most likely cause of failure is something to do with the immersion itself. I wouldn't let the manufacturer fob you off saying the only cause can be due to the cylinder running dry as that bull imo. I've had immersions that have not worked straight out the box...I've also had an immersion fail after a few weeks and ended up replacing it with a titanium aggressive water type and as far as I'm aware it's still going strong.

 

[leiadad]

Thanks for advice Lee, as far as I know it is titanium aggressive water type

 

[Chuck]

@Chuck

3 phase is 3 x 240v and normally no neutral or one neutral

It's very unlikely they would accidentally connect 2 or 3 phases to one side of the immersion to overload and blow

Be more likely that the phases are unbalanced (more load on one side causing a drop)

If the immersion is a star configuration (shared neutral, 3*240V elements), swapping the neutral and one phase by mistake results in 415V across two elements and 240 across the third. Not a mistake a properly qualified and experienced electrician would make, but a possible scenario for the described symptoms.

 

[ShaunCorbs]

If the immersion is a star configuration (shared neutral, 3*240V elements), swapping the neutral and one phase by mistake results in 415V across two elements and 240 across the third. Not a mistake a properly qualified and experienced electrician would make, but a possible scenario for the described symptoms.

But then the immersion wouldn't work fully from day one, would it also trip/ blow some fuses

 

[leiadad]

Thanks chuck, all I know is they come off a contactor before going to immersion, I am pretty sure there is one neutral

 

[MOSSEP]

But then the immersion wouldn't work fully from day one, would it also trip/ blow some fuses

It probably would work form day 1 but burn out early. If you have ever put a 110v light bulb into a normal light fitting you see that it burn really bright for a short while and then dies. The same would happen with an immersion, it would heat the water up very quickly and then pack up!

 

[ShaunCorbs]

It probably would work form day 1 but burn out early. If you have ever put a 110v light bulb into a normal light fitting you see that it burn really bright for a short while and then dies. The same would happen with an immersion, it would heat the water up very quickly and then pack up!

yea were talking about under a day still

 

[MOSSEP]

I don't know, I think it would last longer than that. The only reasons for it to burn out would be over heating, and being in a water cylinder makes for great water cooling! Add to that that the thermostat would probably still turn it on and off means it may not be running all of the time.

 

[Chuck]

yea were talking about under a day still

If the immersion was a 12kW, i.e 3 * 16.7A * 240V the overload current would be 29A. If the supply was protected by 20A fuses (the lowest workable choice) these could take a long time (hours maybe longer) to disconnect. I don't know how long an immersion heater would last when run at 100% (power) overload. My guess would be a few hours but it could be longer or shorter depending on how it was constructed.

I do not claim this is the only explanation, or even the most likely, but I don't think that it can be ruled out on the basis of the information we currently have.

I'd like to reserve judgement until we have some crime-scene photos to look at.